<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      padding: 0;
      margin: 0;
    }
    .yyy{
      width: 500px;
      height: 500px;
      text-align: center;
      background-color: pink;
    }
  </style>
</head>

<body>

  <div class="yyy">
      杨艺宇
  </div>
  <div class="header">
    <p>123</p>
  </div>
  <div class="footer">
    <p>456</p>

  </div>
</body>

</html>